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QUIK STATS (last updated Sep 21, 2020 )
NOTES ABOUT THIS BIOTYPE
In: 2017 New Zealand Plant Protection Society - Weeds.
An evaluation of the resistance of annual and perennial ryegrass to herbicides
M. Gunnarsson1, T.K. James2, R.J. Chynoweth1 and M.P. Rolston1 1Foundation for Arable Research, P.O. Box 23133, Templeton, Christchurch 8445, New Zealand 2AgResearch Ltd., Ruakura Research Centre, Private Bag 3123, Hamilton 3240, New Zealand Corresponding author: Matilda.Gunnarsson@far.org.nz
Abstract Ryegrass, both perennial (Lolium perenne) and annual (L. multiflorum), can be weeds in other arable crops such as wheat (Triticum aestivum). They are generally removed using selective herbicides, but herbicide-resistant perennial and annual ryegrasses have been reported anecdotally. Perennial ryegrass seeds that were suspected to be herbicide resistant were sourced from near Methven, Canterbury. They were evaluated for tolerance to five herbicides and were found to be resistant to all of them. In a separate experiment, annual ryegrass seeds that were suspected to be herbicide resistant were also sourced from near Methven, Canterbury. They were evaluated for tolerance to six different herbicides and were found to be resistant to haloxyfop applied at up to four times label rate but susceptible to clethodim. These results have important implications for growers and advisers throughout New Zealand.
CONTRIBUTING WEED SCIENTISTS
Perennial ryegrass (Lolium perenne) has developed resistance to glyphosate within New Zealand vineyards following many years of herbicide application. The objectives of this work were to confirm resistance within two populations obtained from affected vineyards, and to determine the mechanism of resistance to glyphosate.
Population O was confirmed to have a 25‐fold resistance to glyphosate, whereas population J had a sevenfold resistance. Results of genotyping assays demonstrated a single nucleotide substitution at codon 106 of 5‐enolpyruvylshikimate‐3‐phosphate synthase in population O but not population J. Glyphosate‐resistant and glyphosate‐susceptible populations did not differ in glyphosate absorption. However, in both resistant populations, much more of the absorbed 14C‐glyphosate remained in the treated leaf than occurred in the susceptible population. Significantly more glyphosate was found in the pseudostem region of susceptible plants compared with resistant plants.
Both target‐site and non‐target‐site mechanisms of glyphosate resistance were found in the perennial ryegrass population with 25‐fold resistance, whereas only the non‐target‐site mechanism of resistance was found in the population with sevenfold resistance. This is the first study of the mechanism of glyphosate resistance in perennial ryegrass.